Whats happen when an hybrid android app is closed?

I read a time ago that apps made with html5 dont have the states paused/stopped... because they run at webview so when you close the app they just done.

I have a project in Ionic that I'm facing a strange issue, I have a timer that checks data at webservice and depending the result I show a toast message.

The issue is, when I close the app looks like this timer still, because after a litle time that I just closed the app I receive the toast message, looks like the timer still running in the background.

I would to know how exactly a webview app works when closed both Android/IOS, I'm facing this issue at Android.